5-nitro-3,4-dihydro-1(2H)-naphthalinone is an intermediate for the production of 1,5-naphthalenediamine, which can be obtained from 5-nitro-3,4-dihydro-1(2H)-naphthalinone by amination, aromatization and subsequent hydrogenation. 1,5-naphthalenediamine can be further reacted with phosgene to form 1,5-naphthalene diisocyanate.
Various processes for producing 1,5-naphthalenediamine are already known in the literature. In general, the preparation of 1,5-naphthalenediamine starts from naphthalene, which is suitably substituted. Thus, in JP-A2-07 278 066, the synthesis of 1,5-naphthalenediamine via an amine-bromine exchange in 1,5-bromoaminonaphthalene is described. In this process, the required educt is produced by bromination of 1-nitronaphthalene.
In JP-A2-04 154 745, JP-A2-56 059 738 and DE-A1-2 523 351, the synthesis of 1,5-naphthalenediamine in combination with 1,8-naphthalenediamine by reduction of a mixture of 1,5- and 1,8-dinitronaphthalene is described. The synthesis of 1,5-naphthalenediamine by alkaline hydrolysis of disodium naphthalene-1,5-disulfonate and subsequent reaction with ammonia is described in DE-C1-3 840 618.
All the above-described processes have the disadvantage that the product, or an intermediate product produced in the course of the process, is obtained in the form of a mixture of isomers which in addition to the 1,5-isomers contains further isomers which have to be separated off. Moreover, the process described in DE-C1-3 840 618, in particular, proceeds under very drastic and corrosive reaction conditions.